Commercial walk-in coolers, such as those commonly found in convenience stores and commercial food storage facilities such as supermarkets, are typically constructed of insulating wall, ceiling and floor panels that are fastened together. The panel ends are shaped to fit together in tongue and groove fashion and are provided with latch type fastening means for drawing and holding adjacent panels together. The latches themselves commonly comprise a hook and cam assembly inside a casing that is mounted to one panel for latching engagement with a pin assembly inside a casing that is mounted to an adjacent panel. There are two main types of panel fasteners, nail-in-place and winged. Examples of these fasteners are shown in U.S. Pat. Nos. 3,784,240 and 3,671,006, respectively. The winged fasteners are usually mounted by being foamed in place using methods similar to the one shown in U.S. Pat. No. 5,212,924. Foam is injected inside the panel and as it hardens, the fasteners become secured in place. An undesirable side effect of the foam-in-place method is that foam often leaks into the casing of the hook. After foam hardening, it presents an obstacle to the movement of the hook.
The hook and cam assembly includes a C-shaped leaf spring that operates in a clutch like action by transferring torque from the cam to the hook. The advantage of using a C-shaped spring is that it is provides sufficiently high frictional resistance for driving the hook while also being easy to assemble by being clipped onto the cam.
During actuation of the latch, the cam turns bringing the spring into engagement with the hook. This causes the spring to shift in a direction opposite to the direction in which the hook is driven. The pressure caused by the shifting of the spring, combined with the compression of the spring, causes a significant portion of the angular flexing of the spring to occur over a very short span. This often results in the spring becoming crimped. Such crimping has been a significant and persistent problem as it weakens the resilience of the spring and reduces its frictional engagement with the hook. As a result, the spring often becomes incapable of transferring sufficient torque to re-engage the hook with the pin. This is especially true where the path of the hook is partially blocked with debris or hardened foam.
It is thus seen that a need has long existed for a panel fastener with a cam and hook assembly of the type that employs a C-shaped spring that is not susceptible to being crimped and that is capable of transferring high and consistent drive torque to the hook. Accordingly, it is the provision of such that this invention is primarily directed.